Recently, a fuel cell (fuel cell stack) is used as a power source of a vehicle. As for a fuel cell system executing control of power generation amount in such a fuel cell, various kinds of techniques are disclosed.
A technique of consuming the hydrogen by increasing the power generation amount in the fuel cell at the time of deceleration of the vehicle is disclosed in Japanese Patent Application aid-open under No. 2002-289238 (Reference-1), for example. A technique of consuming the hydrogen by continuing to generate electricity even after stopping supplying the hydrogen at the time of stopping of the fuel cell is disclosed in Japanese Patent Application Laid-open under No. 2004-79451 (Reference-2) and No. 2004-127748 (Reference-3). Additionally, in Japanese Patent Application Laid-open under No. 7-75214 (Reference-4), there is disclosed a technique of generating the electricity of the fuel cell at outputable power when required power of the fuel cell is larger than the outputable power thereof. Moreover, a technique of executing control to maintain a pressure difference between a cathode electrode and an anode electrode of the fuel cell within an allowable range is disclosed in Japanese Patent Application Laid-open under No. 8-45527 (Reference-5).
However, in the above technique according to Reference-1, by increase of the power generation amount at the time of the deceleration of the vehicle, the power amount equal to or larger than the power generation amount (hereinafter simply referred to as “allowable power generation amount”) which the fuel cell can stably generate is outputted, and thus the hydrogen gas becomes insufficient. Thereby, the fuel cell is sometimes deteriorated. In addition, in the techniques according to Reference-2 to Reference-5, at the time of movement from an accelerating state to a decelerating state in the vehicle, the hydrogen more than originally needed is supplied to the fuel cell, and the large amount of non-reacted hydrogen is sometimes generated.